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• THREE-DIMENSIONAL SPECTRAL RADIATIVE HEAT TRANSFER CALCULATION IN A CYLINDRICAL MODEL COMBUSTOR USING THE DISCRETE ORDINATES METHOD  download article

W. Krebs
Lehrstuhl und Institut fur Thermische Strömungsmaschinen Unversität Karlsruhe, Karlsruhe, Germany

R. Koch
Lehrstuhl und Institut fur Thermische Strömungsmaschinen Unversität Karlsruhe, Karlsruhe, Germany

H.-J. Bauer
Lehrstuhl und Institut für Thermische Strömungsmaschinen, Universität Karlsruhe, Kaiserstrabe 12, D-76128 Karlsruhe, Germany

S. Wittig
Lehrstuhl und Institut fur Thermische Strömungsmaschinen Unversität Karlsruhe, Karlsruhe, Germany

ABSTRACT

Among the different methods applied for calculating heat transfer in combustors, the Discrete Ordinates Method (DOM) is considered to be the most promising one with respect to high accuracy and little computer time consumption. In this paper the DOM is validated for the first time to predict 3-dimensional non luminous radiative heat transfer in a cylindrical propane fired model combustor featuring steep gradients of temperature and concentration. The radiation calculations are carried out in connection with a CFD-Code providing data of the temperature field and the concentration distribution of radiative active species. The radiation calculations are performed on a spectral basis using narrow-band models to represent accurately the radiative properties of combustion gases. Additional terms accounting for angular redistribution are avoided by formulating the discrete direction vector Ω_m in cylindrical coordinates. The different S_n-approximations (S₂, S₄ S₈) applied are evaluated by comparing the calculated spectra to measured spectra and spectra obtained from 1-D-calculations which serve as reference data. It is pointed out, that radiative transfer calculations through the reaction zone of the combustor are most critical due to the steep gradients of scalar variables. However, using a fine calculational grid of 18998 grid points, the S₄-approximation already yields accurate results which are almost as accurate as the results determined by application of the S₈-approximation.

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